74 nitrosyl chloride, reaction with alkenes

Reaction with a cyclic amine in the presence of a base and at ambient temperature forms alkene. Thus, nitrosyl chloride reacts with aziridine to form ethylene and nitrous oxide ... 

Aziridines can undergo loss of a nitrogen atom in a number of ways and this process is frequently stereospecific in terms of the alkene formed. For example, the reaction of aziridines, e.g. (268), with nitrosating agents such as nitrosyl chloride or methyl nitrite results in the formation of alkenes wit.h greater than 99% stereoselective deamination (64JOC1316). Such transformations proceed via N- nitrosoaziridine intermediates which are isolable at temperatures below -20 °C, but which decompose to the observed products at higher temperatures. 

The alkenes are distinguished from the alkanes by their solubility in concentrated sulphuric acid and their characteristic reactions with dilute potassium permanganate solution and with bromine. Characterisation may be based upon the determination of their physical and/or spectral properties. Characterisation by way of solid adducts with nitrosyl chloride has been quite widely used in the terpene field the preparation of adducts with 2,4-dinitrobenzenesulphenyl chloride is described below (see also Section 8.1.1, p. 1128). 

A reaction corresponding to Eq. (5-30) is the addition of nitrosyl chloride to alkenes such as cyclohexene or styrene [84, 85]. The reaction seems to be faster in polar solvents e.g. nitrobenzene and trichloromethane) than in less polar solvents e.g. toluene and tetrachloromethane). This is consistent with the view that the reaction involves an electrophilic attack of NO —Cl . The reaction was, however, also found to be very slow in diethyl ether. Presumably, this is due to strong bonding of the NO+ cation to the ether oxygen atom [84]. 

With excess nitrosyl chloride, a chloronitro product is obtained in certain cases, a wide variety of ste-roid-5-enes giving 5a-chloro-6p-nitro derivatives in good yield (CH2CI2/CG4, to 0 C, 2-24 h). Nitryl chloride adds to terminal alkenes (56-80%) and to aoylic acid derivatives (refs. 239,240 and references cited therein) at temperatures close to amlrient. The reaction iq>peais to be a radical one, the NO2 entering the terminal position whatever the electronic requirement of the alkene. 

The site-selective addition of nitrosyl chloride to an f-configurated double bond, determined by kinetic studies18 with acyclic and cyclic (E)- and (Z)-alkenes in chloroform or by the reactions with (Z,E, )-1,5,9-cyclododecatriene19 and (Z,E)-, 5-cyclodecadiene"fl in dichloromethane, can be explained in terms of conformational stability in the four-centered transition state or by a syn-type addition however, the configuration of the products of such reactions was not elucidated. 

Electron-deficient alkenes (e.g., NCHC=C(COOMe)2) can be aziridinated with 0-(aryl-sulfonyl)hydroxylamines <9lCOS(7)469>. The reaction is believed to involve a Michael addition followed by cyclization with expulsion of a sulfonate anion. Less electrophilic alkenes react in lower yield but with high stereoselectivity (Equation (2)). The chiral catalyst prepared from an optically active bisoxazoline and Cu(I)triflate is effective in promoting the enantioselective aziridination of alkenes <93JA5328>. The addition of nitrosyl chloride to alkenes, which are especially susceptible to... 

Treatment of an aziridine with nitrosyl chloride, S-nitro-TV-nitrosocarbazole or methyl nitrite leads to the formation of an alkene and nitrous oxide (equation 76) " an intermediate iV-nitroso derivative was isolated at low temperatures. The deamination of cis-and frflBJ-2,3-dimethylaziridine gave the corresponding ds- and fra J-2-butenes with complete stereospecificity in each case. The reaction was found to be first order with respect to the A nitroso intermediate and the transition state was suggested to involve simultaneous cleavage of both C—bonds. A similar decomposition... 

First ionization potentials of representative acyclic alkenes have been shown to correlate with log rei (alkene relative reactivities) for the reactions with dichlorocarbene, nitrosyl chloride, and osmium tetroxide. Each reaction gives a single line of correlation, which includes all alkenes studied, regardless of the degree of substitution. 

---